A cellular mobile radio system may comprise a plurality of cells. Each cell has at least one base station for simultaneous communication with a number of mobile stations. Signal transmission is effected between the base station of a cell and the mobile stations served by the base station in said cell by transmitting and receiving radio signals, for instance when the mobile stations are used for calling purposes.
It is known to have a so-called fixed frequency plan in mobile radio systems which utilize FDMA and/or TDMA in order to obtain a large number of radio communication channels. That is, signals are transmitted in each cell between the base station and the mobile stations on a given number of determined radio frequencies. For instance, a cell can be assigned twenty different signal transmission frequencies. The cells are divided logically into groups, with several cells in each group. The cells within one group utilize different radio frequencies, although cells in different groups may utilize the same radio frequencies.
An alternative to a fixed frequency plan for FDMA and TDMA is the adaptive or dynamic assignment of channels/frequencies. All, or at least some, of the available radio frequencies and, in the case of TDMA, also the time slots on the radio frequencies, constitute a common resource for all cells, or at least for several neighbouring cells. One example of dynamic channel assignment is described in U.S. Pat. No. 4,736,453.
An alternative to FDMA and TDMA when desiring a large number of radio communication channels is CDMA, Code Division Multiple Access. In a mobile radio system in which CDMA is applied and in which traffic is not unduly excessive, it is conceivable to use just a single radio frequency, or rather a single radio frequency band. This radio band has no fixed division of separate time slots which are allocated to separate stations. Instead the whole radio band can be used simultaneously in different ways by all of the mobile stations. An example of CDMA is described in EP 0189695.
Power regulation in mobile radio systems with analogue information transmission is of a relatively simple kind and the adjustment is a relatively rough adjustment. See in this respect U.S. Pat. No. 4,485,486. According to one proposed standard for digital mobile radio systems, such as GSM in Europe and EIA/TIA IS-54 in the U.S.A., protocol is found for the transmission of measurement information and commands concerning transmission power. As is well known, there is at present no published technology for regulating power transmission in digital mobile telephony systems with respect to prevailing radio-signal propagation conditions, signal disturbance, system traffic, etc.